Phage insensitive streptococcus thermophilus

Abstract

Bacteriophage Insensitive Mutants (BIMs) of three Streptococcus thermophilus parent strains were generated and characterized for phage sensitivity, sedimentation rate, cell chain length, phage adsorption and CRISPR loci alterations. Several BIMs showed an altered sedimentation phenotype as well as an increase cell chain length, reduced phage sensitivity, reduced phage adsorption and 100% identity in three CRISPR loci. The results show that the derived BIMs have become phage-resistant through a mechanism other than CRISPR.

The invention claimed is: 
     
       1. A bacteriophage insensitive mutant of a parent strain of  Streptococcus thermophilus , wherein the bacteriophage insensitive mutant is generated by exposing the  Streptococcus thermophilus  parent strain to an isolated bacteriophage wherein the bacteriophage insensitive mutant is suitable for use in food or feed, and wherein the bacteriophage insensitive mutant has an increased sedimentation rate and/or an increased chain formation compared to the parent strain, wherein the parent strain is deposited as CBS136255, CBS136256 or CBS138555. 
     
     
       2. The bacteriophage insensitive mutant according to  claim 1 , having a phage adsorption percentage of 60% or less, 55% or less, or 50% or less compared to the phage adsorption of the parent strain. 
     
     
       3. The bacteriophage insensitive mutant according  claim 2 , wherein the bacteriophage comprises at least one nucleotide sequence selected from the group consisting of SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 3, SEQ ID NO: 4 and SEQ ID NO: 5. 
     
     
       4. A starter culture composition suitable for inoculation of a medium to be fermented on an industrial scale comprising the bacteriophage insensitive mutant according to  claim 1 . 
     
     
       5. The starter culture composition according to  claim 4 , wherein the starter culture composition is frozen, freeze dried, or in liquid form. 
     
     
       6. A container comprising the bacteriophage insensitive mutant according to  claim 1 , or comprising a starter culture composition comprising the mutant of  claim 1 . 
     
     
       7. The bacteriophage insensitive mutant of  claim 1 , which has reduced phage adsorption, compared to the phage adsorption of the parent strain, to one or more phages that comprise a nucleotide sequence selected from the group consisting of SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 3, SEQ ID NO: 4 and SEQ ID NO: 5 or that comprise a nucleotide sequence having at least 80% sequence identity with the nucleotide sequence selected from the group consisting of SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 3, SEQ ID NO: 4 and SEQ ID NO: 5. 
     
     
       8. The bacteriophage insensitive mutant of  claim 7 , which has reduced phage adsorption, compared to the phage adsorption of the parent strain, to one or more that comprise a nucleotide sequence having at least 85% sequence identity with the nucleotide sequence selected from the group consisting of SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 3, SEQ ID NO: 4 and SEQ ID NO: 5. 
     
     
       9. The bacteriophage insensitive mutant of  claim 8 , wherein the parent strain is bacteriophage sensitive. 
     
     
       10. The bacteriophage insensitive mutant of  claim 9 , which mutant has CRISPR loci which is identical to the CRISPR loci of the bacteriophage sensitive  Streptococcus thermophilus  parent strain. 
     
     
       11. The starter culture composition of  claim 4 , in combination with further comprising a cryoprotectant. 
     
     
       12. The starter culture composition of  claim 4 , further comprising  L. bulgaricus  or  Lactobacillus delbrueckii  subsp.  bulgaricus.    
     
     
       13. The bacteriophage insensitive mutant of  claim 1  which has an increased sedimentation rate compared to the parent strain. 
     
     
       14. The bacteriophage insensitive mutant of  claim 1  which has an increased chain formation compared to the parent strain. 
     
     
       15. A starter culture composition suitable for inoculation of a medium to be fermented on an industrial scale comprising the bacteriophage insensitive mutant according to  claim 7 . 
     
     
       16. The starter culture composition of  claim 15 , further comprising  L. bulgaricus  or  Lactobacillus delbrueckii  subsp.  bulgaricus.    
     
     
       17. A dairy product comprising the starter culture composition of  claim 4 . 
     
     
       18. A dairy product comprising the starter culture composition of  claim 5 . 
     
     
       19. The dairy product of  claim 17 , which is a fermented milk product or cheese. 
     
     
       20. The dairy product of  claim 18 , which is a fermented milk product or cheese.